1. Field of the Invention
The subject invention generally pertains to HVAC unit ventilators such those often used in classrooms and hotels. The invention more specifically pertains to a damper assembly that apportions the amount of outside air and return air to such a ventilator.
2. Description of Related Art
HVAC unit ventilators typically include a blower, heat exchanger, and a damper assembly for independently controlling the heating or cooling of separate rooms of a multi-room building such as a school or hotel. The building may have numerous unit ventilators whose individual heat exchangers receive their heat or cooling energy from a commonly shared source, such as a central boiler or chiller. When a unit ventilator includes a DX coil for cooling, the coil is usually associated with its own condenser rather than a central one.
Unit ventilators are typically mounted against an outer wall of the building so that they can draw in fresh outside air when the outdoor temperature and humidity are favorable and/or draw in return air from within the room. The damper assembly controls the proportions of outside air and return air. After the outside air and/or return air is drawn into the ventilator, the blower forces the air across a filter and the heat exchanger to create a current of clean supply air that discharges into the room for heating, cooling, or ventilation.
Damper assemblies of unit ventilators or other air-mixing equipment often include multiple dampers interconnected by complicated linkages or gears. Examples of such multi-damper systems are disclosed in U.S. Pat. Nos. 2,220,355 and 4,336,748. The linkages and gears for driving and coordinating the movement of the dampers can adversely affect the unit's overall cost and reliability. U.S. Pat. No. 1,782,711 discloses a single damper; however, it also is driven by a linkage assembly.
U.S. Pat. Nos. 607,900 and 2,755,072 each discloses what appears to be a single damper for mixing indoor and outdoor air. These dampers, however, are quite planar, and although that may be fine for their particular application, simple flat dampers do not work well for unit ventilators, which tend to be rather long and narrow. Long, flat damper blades tend to twist and bend, thus they do not seal very well.
Moreover, since unit ventilators are usually installed in the same room as the occupants, the amount of space consumed by the ventilator is a major concern. If a unit ventilator's blower, heat exchanger, damper system and filter are simply stacked one atop the other, the resulting unit can be unreasonably large and bulky.
Consequently, a need exists for a unit ventilator that is simple, robust and compact.